Polishing slurry for silicon oxide, additive liquid and polishing method

ABSTRACT

The polishing slurry of the invention is a polishing slurry for polishing a silicon oxide film on polysilicon, which contains an abrasive, polysilicon polishing inhibitor, and water. As the polishing inhibitor, it is preferable to use (1) a water-soluble polymer having a N-monosubstituted or N,N-disubstituted skeleton substituted by any member selected from the group consisting of acrylamide, methacrylamide, and α-substituted derivatives thereof, (2) polyethylene glycol, (3) an oxyethylene adduct of an acetylene-based diol, (4) a water-soluble organic compound having an acetylene bond, (5) an alkoxylated linear aliphatic alcohol, or (6) a copolymer containing polyvinyl pyrrolidone or vinyl pyrrolidone. There is provided a polishing method which is capable of polishing a silicon oxide film on a polysilicon film at a high speed, and inhibiting the progress of polishing of a polysilicon film in exposed parts in the manufacturing method for a semiconductor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a polishing slurry preferably used in theplanarization process for dielectrics on substrate surfaces, which is amanufacturing technique for semiconductor devices, and particularlyrelates to a polishing slurry for silicon oxide on polysilicon, anadditive liquid used in the polishing slurry, and a polishing methodusing the polishing slurry.

2. Description of the Related Art

In the present ULSI semiconductor device manufacturing processes,processing techniques for achieving higher density and fineness havebeen developed. Among them, CMP (Chemical Mechanical Polishing)technique is becoming an essential technique in the manufacturingprocess for semiconductor devices, for planarization of interlayerdielectrics, shallow trench isolation, formation of plugs or buriedmetal wiring, and other purposes.

In the manufacturing process for semiconductor devices, as chemicalmechanical polishing slurries for the planarization of inorganicdielectric layers, a fumed silica polishing slurry, colloidal silicapolishing slurry, and cerium oxide polishing slurry have been generallystudied. Examples of inorganic dielectric layers include a silicon oxidedielectric formed by a plasma-CVD method, a low-pressure-CVD method, orother method. Fumed silica is produced from silicon tetrachloride byheat decomposition or other method, and the particles are grown to beused as an abrasive in a polishing slurry. Colloidal silica used to bemade from water glass, but alkali components derived from water glassremains in colloidal silica, thus it contains too much metal impuritiesfor semiconductor applications. Afterward, a method for manufacturingcolloidal silica from alkoxide was established, which has allowed themanufacture of high purity products, and commercialization of colloidalsilica which can be used as an abrasive for semiconductors. In order touse such a silica polishing slurry for polishing silicon oxide for asemiconductor, such as silicon oxide or borosilicate, the pH of theslurry is often adjusted to alkaline for increasing the polishing rate.

On the other hand, cerium oxide particles have lower hardness and areless prone to give scratches on the polishing surface in comparison withsilica particles or alumina particles. Further, since cerium oxidepolishes silicon oxide at a high polishing rate, the applicable pH rangeis not particularly limited. In recent years, a CMP polishing slurryusing a high purity cerium oxide abrasive is used for semiconductorapplications. The technique is, for example, disclosed in JapanesePatent Application Laid-Open No. 10-106994. Another known technique isto add an additive to a cerium oxide polishing slurry for controllingthe polishing rate thereof to increase global flatness. The technique isdisclosed, for example, in Japanese Patent Application Laid-Open No.8-22970.

Along with the progress of semiconductor device structures, CMPprocesses are diversified. After the generation of design rule 0.25 μm,shallow trench isolation is used for isolating devices in an integratedcircuit. In shallow trench isolation, CMP is used for removing thesurplus parts of a silicon oxide film formed on the substrate. In orderto stop polishing by CMP, a stopper film which is polished at a low rateis formed under the silicon oxide film. The stopper film is typicallymade of silicon nitride, and the polishing rate ratio between thesilicon oxide film and the stopper film is preferably large. Such atechnique of using a stopper for stopping polishing is used in otherapplications as well as shallow trench isolation. Besides shallow trenchisolation, a stopper may be used, for example, in formation of a plug orthe like wherein the surplus parts of a film must be removed by CMP forplanarization.

SUMMARY OF THE INVENTION

Silicon nitride has been commercialized as a stopper for shallow trenchisolation because it has high hardness and is readily controllable inpolishing rate. Stoppers other than silicon nitride may be possible aslong as they are films controllable in their polishing rate. Forexample, a barrier metal for Cu wiring also serves as a stopper in CMP.In addition, polysilicon (polycrystalline silicon) will be usable as astopper if the polishing rate thereof is sufficiently controllable.

Polysilicon, which is used as a conductive material for a transistorgate or the like, can be used in different applications from siliconnitride if a CMP technique for using polysilicon as a stopper isestablished. However, it has been difficult to control polysilicon to adegree where it can be used as a stopper, or to achieve a sufficientlylarge polishing rate ratio between a film to be polished and polysiliconeither with a silica polishing slurry or a cerium oxide polishingslurry.

The object of the invention is to provide a polishing slurry for siliconoxide on polysilicon which achieves a sufficiently large polishing rateratio between silicon oxide and polysilicon for making polysiliconapplicable as a stopper, and a polishing method using the same forpolishing a semiconductor substrate or the like.

The invention relates to [1] a polishing slurry for silicon oxide forpolishing a silicon oxide film on polysilicon, which contains anabrasive, a polysilicon polishing inhibitor, and water.

Further, the invention relates to [2] the polishing slurry for siliconoxide according to [1], wherein the ratio of the polishing rate forsilicon oxide to that for polysilicon is 10 or more.

Further, the invention relates to [3] the polishing slurry for siliconoxide according to [1] or [2], wherein the polysilicon polishinginhibitor is a water-soluble polymer having a N-monosubstituted orN,N-disubstituted skeleton substituted by any member selected from thegroup consisting of acrylamide, methacrylamide, and α-substitutedderivatives thereof.

Further, the invention relates to [4] the polishing slurry for siliconoxide according to [3], wherein the water-soluble polymer is a polymeror copolymer containing at least one selected from the group consistingof a polymerizable monomer represented by the following formula (I) anda polymerizable monomer represented by the following general formula(II).

(In the general formula (I), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, and R₂ and R₃ each independentlyrepresents a hydrogen atom, alkyl chain of C₁ to C₁₈, methylol group, oracetyl group with the proviso that the case where both of themsimultaneously represent a hydrogen atom is excluded.)

(In the general formula (II), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, R₄ represents a morpholino group,thiomorpholino group, pyrrolidino group, or piperidino group.)

Further, the invention relates to [5] the polishing slurry for siliconoxide according to [1] or [2], wherein the polysilicon polishinginhibitor is polyethylene glycol.

Further, the invention relates to [6] the polishing slurry for siliconoxide according to [1] or [2], wherein the polysilicon polishinginhibitor is an oxyethylene adduct of a acetylene-based diol.

Further, the invention relates to [7] the polishing slurry for siliconoxide according to [1] or [2], wherein the polysilicon polishinginhibitor is at least either of the compound represented by thefollowing general formula (III) and the compound and represented by thefollowing general formula (IV).

[Formula 3]R¹—C≡C—R²  (III)

(In the general formula (III), R¹ represents a hydrogen atom orsubstituted or unsubstituted alkyl group having 1 to 5 carbon atoms, R²represents a substituted or unsubstituted alkyl group having 4 to 10carbon atoms.)

(In the general formula (IV), R³to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)

Further, the invention relates to [8] the polishing slurry for siliconoxide according to [1] or [2], wherein the polysilicon polishinginhibitor is an alkoxylated linear aliphatic alcohol.

Further, the invention relates to [9] the polishing slurry for siliconoxide according to any of [1] through [7], which contains two or moretypes of the polysilicon polishing inhibitor.

Further, the invention relates to [10] the polishing slurry for siliconoxide according to [9], wherein the polysilicon polishing inhibitorincludes two or more compounds selected from the

-   -   water-soluble polymer,    -   polyethylene glycol,    -   an oxyethylene adduct of an acetylene-based diol,    -   a compound represented by the general formula (III),    -   a compound represented by the general formula (IV), and    -   an alkoxylated linear aliphatic alcohol.

Further, the invention relates to [11] the polishing slurry for siliconoxide according to any of [3] through [10], wherein the content of thepolysilicon polishing inhibitor is 0.005% by mass or more and 2% by massor less.

Further, the invention relates to [12] the polishing slurry for siliconoxide according to any of [3] through [11], wherein the pH is 5.0 to8.0.

Further, the invention relates to [13] the polishing slurry for siliconoxide according to any of [1] through [12], which contains at least oneselected from polyacrylic acid, polyacrylate, and a copolymer containingacrylate.

Further, the invention relates to [14] the polishing slurry for siliconoxide according to any of [1] through [13], wherein the abrasivecontains cerium oxide.

Further, the invention relates to [15] the polishing slurry for siliconoxide according to [1] or [2], wherein the polysilicon polishinginhibitor contains polyvinyl pyrrolidone or a copolymer containing vinylpyrrolidone.

Further, the invention relates to [16] the polishing slurry for siliconoxide according to [15], wherein the content of the polysiliconpolishing inhibitor is 0.005 to 5% by mass.

Further, the invention relates to [17] the polishing slurry for siliconoxide according to [15] or [16], wherein the pH is 5.0 to 12.0.

Further, the invention relates to [18] the polishing slurry for siliconoxide according to any of [15] through [17], which contains at least oneselected from polyacrylic acid, polyacrylate, and a copolymer containingacrylate.

Further, the invention relates to [19] the polishing slurry for siliconoxide according to any of [15] through [18], wherein the abrasivecontains cerium oxide.

Further, the invention relates to [20] the polishing slurry for siliconoxide according to any of [1] through [19], wherein the content of atleast one selected from polyacrylic acid, polyacrylate, and a copolymercontaining acrylate is 0.01 to 5% by mass.

Further, the invention relates to [21] the polishing slurry for siliconoxide according to any of [1] through [20], wherein the abrasivecontains silicon oxide.

Further, the invention relates to [22] a method for polishing asemiconductor substrate using the polishing slurry for silicon oxideaccording to any of [1] through [21].

Further, the invention relates to [23] an additive liquid for polishingslurry used in a polishing slurry for polishing a silicon oxide film onpolysilicon, which contains a polysilicon polishing inhibitor and water.

Further, the invention relates to [24] the additive liquid for polishingslurry according to [23], wherein the polysilicon polishing inhibitor isa water-soluble polymer having a N-monosubstituted or N,N-disubstitutedskeleton substituted by any member selected from the group consisting ofacrylamide, methacrylamide, and α-substituted derivatives thereof.Further, the invention relates to [25] the additive liquid for polishingslurry according to [24], wherein the water-soluble polymer is a polymeror copolymer containing at least one selected from the group consistingof a polymerizable monomer represented by the following formula (I) andapolymerizable monomer represented by the following general formula(II).

(In the general formula (I), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, and R₂ and R₃ each independentlyrepresents a hydrogen atom, alkyl chain of C₁ to C₁₈, methylol group, oracetyl group with the proviso that the case where both of themsimultaneously represent a hydrogen atom is excluded.)

(In the general formula (II), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, R₄ represents a morpholino group,thiomorpholino group, pyrrolidino group, or piperidino group.)

Further, the invention relates to [26] the additive liquid for polishingslurry according to [23], wherein the polysilicon polishing inhibitor ispolyethylene glycol.

Further, the invention relates to [27] the additive liquid for polishingslurry according to [23], wherein the polysilicon polishing inhibitor isan oxyethylene adduct of an acetylene-based diol.

Further, the invention relates to [28] the additive liquid for polishingslurry according to [23], wherein the polysilicon polishing inhibitor isat least either of the compound represented by the following generalformula (III) and the compound and represented by the following generalformula (IV).

[Formula 7]R¹—C≡C—R²  (III)

(In the general formula (III), R¹ represents a hydrogen atom orsubstituted or unsubstituted alkyl group having 1 to 5 carbon atoms, R²represents a substituted or unsubstituted alkyl group having 4 to 10carbon atoms.)

(In the general formula (IV), R³ to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)

Further, the invention relates to [29] the additive liquid for polishingslurry according to [23], wherein the polysilicon polishing inhibitor isan alkoxylated linear aliphatic alcohol.

Further, the invention relates to [30] the additive liquid for polishingslurry according to [23], which contains two or more types of thepolysilicon polishing inhibitor.

Further, the invention relates to [31] the additive liquid for polishingslurry according to [30], wherein the polysilicon polishing inhibitorincludes two or more compounds selected from the water-soluble polymer,polyethylene glycol, an oxyethylene adduct of an acetylene-based diol, acompound represented by the general formula (III), a compoundrepresented by the general formula (IV), and an alkoxylated linearaliphatic alcohol.

Further, the invention relates to [32] the additive liquid for polishingslurry according to any of [23] through [31], which further contains atleast one selected from polyacrylic acid, polyacrylate, and a copolymercontaining acrylate.

Further, the invention relates to [33] a polishing method using thepolishing slurry for silicon oxide according to any of [1] through [21],wherein the object to be polished is held against a polishing pad withthe surface thereof to be polished facing the polishing pad, andpolished by being slid relative to the polishing pad while the polishingslurry is supplied between the polishing pad and the surface to bepolished.

The invention provides a polishing slurry and a polishing method whichare capable of polishing a silicon oxide film on a polysilicon film at ahigh speed, and inhibiting the progress of polishing of a polysiliconfilm in exposed parts in a CMP technique in the manufacturing process ofa semiconductor in which a silicon oxide film is polished.

Disclosure of the invention is related to the subject described inJapanese Patent Application No. 2005-327422 which was filed on Nov. 11,2005, and the disclosure of which is incorporated herein by reference.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment of the invention is described in detail below.

As a result of the eager investigation by the inventors of the presentinvention concerning the polishing of a silicon oxide film on apolysilicon film in the planarization process of a semiconductor, it hasbeen found that a polishing slurry comprising an abrasive, water, and ainhibitor for inhibiting polishing of a polysilicon film is capable ofkeeping a high polishing rate for a silicon oxide film and a lowpolishing rate for a polysilicon film, and thereby achieving a highpolishing rate ratio (selective ratio) between them. Thus the presentinvention has been accomplished. It has been also found that theselective ratio is increased by adjusting the pH of the polishingslurry.

The abrasive used in the invention may be cerium oxide, silicon oxide,or the like, and is preferably cerium oxide. Cerium oxide particles arenot limited as to their manufacturing method, but the average primaryparticle diameter of cerium oxide is preferable 5 nm or more and 300 nmor less. This is because, regarding a cerium oxide polishing slurry usedfor polishing of a silicon oxide film formed by a TEOS-CVD method or thelike, cerium oxide having a larger primary particle diameter and lesscrystal distortion or higher crystallinity allows faster polishing, buttends to give polishing scratches. The term primary particles refers toparticles corresponding to crystallites surrounded by grain boundarieswhich are measured and observed with a SEM (scanning electronmicroscope).

In the invention, the method for preparing cerium oxide powder may besintering of a cerium compound such as carbonate, nitrate, sulfate, oroxalate, or oxidation with hydrogen peroxide or the like. The sinteringtemperature is preferably 350° C. or higher and 900° C. or lower. Sincecerium oxide particles prepared by the above-described methods tend tocause aggregation, they are preferably pulverized by a mechanical means.As a pulverizing method, a dry milling method by a jet mill or the like,or a wet milling method with a planet bead mill or the like ispreferable.

The median value of the secondary particle diameter of the abrasive ispreferably 0.03 to 0.5 μm, and more preferably 0.05 to 0.3 μm. This isbecause that if the median value of the secondary particle diameter isless than 0.03 μm, the polishing rate tends to be low, and if more than0.5 μm, the abrasive tends to give polishing scratches on the filmsurface to be polished.

The abrasive is dispersed in water to obtain a slurry. The method fordispersion may be dispersion with an ordinary stirrer, or may use ahomogenizer, ultrasonic disperser, wet ball mill or the like.

The concentration of the abrasive in the polishing slurry is notlimited, but preferably in the range of 0.1% by mass or more and 20% bymass or less, more preferably in the range of 0.2% by mass or more and10% by mass or less, and particularly preferably in the range of 0.5% bymass or more and 5% by mass or less from the viewpoint of manageabilityof the dispersion liquid (slurry).

The slurry may contain a dispersant for the abrasive. Since thedispersant for the abrasive is used for polishing of a semiconductordevice, the content of alkali metals such as sodium and potassium ions,halogens, and sulfur in the dispersant is preferably 10 ppm or less. Apreferable example is a polymer dispersant containing an acrylic acidammonium salt as a copolymerization component.

The addition amount of the dispersant is preferably in the range of 0.01parts by mass or more and 5.0 parts by mass or less relative to 100parts by mass of the abrasive particles in consideration of therelationship between the dispersibility of the particles in thepolishing slurry and prevention of settling, and the relationshipbetween polishing scratches and the addition amount of the dispersant.The weight average molecular weight of the dispersant is preferably 100to 50,000, and more preferably 1,000 to 10,000. This is because if themolecular weight of the dispersant is less than 100, a sufficientpolishing rate is hard to be achieved during polishing of a siliconoxide film, and if the molecular weight of the dispersant is more than50,000, the viscosity tends to be high, and the preservation stabilityof the polishing slurry tends to decrease. The weight average molecularweight is a value determined by gel permeation chromatography, andconverted to standard polystyrene.

Since the abrasive in the thus prepared polishing slurry for siliconoxide of the invention (hereinafter also referred to as polishingslurry) has a particle diameter distribution, 99% by volume (D99) of thewhole particles is preferably 1.0 μm or less. If D99 is more than 1.0μm, many scratches (polishing scratches) may occur.

The median value of the secondary particle diameter of the abrasive inthe polishing slurry) may be determined by a light scattering methodusing, for example, a particle size analyzer (e.g., Mastersizer MicroPlus, manufactured by Malvern Instruments).

The content of coarse particles of 3 μm or more in the total solidcontent in the polishing slurry is preferably lower. When the content ofparticles of 3 μm or more is 500 ppm or less relative to the total solidcontent, it is preferable because the scratch reduction effect isevident. When the content of particles of 3 μm or more is 200 ppm orless relative to the total solid content, it is more preferable becausethe scratch reduction effect is higher. When the content of particles of3 μm or more is 100 ppm or less relative to the total solid content, itis further preferable because the scratch reduction effect is highest.

The content of large particles of 3 μm or more is determined by massdetermination of particles captured by a filter having pore diameter of3 μm. The means for reducing the content of large particles may befiltration or classification, but is not limited to them.

The polysilicon film polishing inhibitor of the invention is preferablya nonionic water-soluble polymer. The reason is as follows: in ameasurement of zeta potential on the surface of a silicon oxide film,which is to be polished by the polishing slurry of the invention, anegative zeta potential of about −20 mV or less is indicated in a largepH range, while a polysilicon (polycrystalline silicon) film, which isto be hindered from being polished, has a pH of 8 or less and a zetapotential of about −10 mV or less, which is relatively close to 0. Anonionic water-soluble polymer is considered to more readily adhere tothe surface of a polysilicon film than the surface of a silicon oxidefilm.

The weight average molecular weight of the water-soluble polymer ispreferably 500 or more and 3,000,000 or less, and more preferably 1,000or more and 1,000,000 or less. This is based on the assumption thatthose having a higher weight average molecular weight are more effectivein inhibiting polishing upon adhesion to the surface of a polysiliconfilm. However, if the weight average molecular weight is excessive, theviscosity of the polishing slurry increases, which causes defects suchas sedimentation of the abrasive. Accordingly, the lower limit ispreferably 500 or more, more preferably 1,000 or more, and particularlypreferably 2,000 or more. The upper limit is preferably 50,000 or less,more preferably 20,000 or less, and particularly preferably 10,000 orless.

Typical examples of the polysilicon film polishing inhibitor includewater-soluble polymers group having a N-monosubstituted orN,N-disubstituted skeleton substituted by any member selected from thegroup consisting of acrylamide, methacrylamide, and α-substitutedderivatives thereof.

Among the water-soluble polymers, a polymer or copolymer using at leastone selected from the polymerizable monomer represented by the followinggeneral formulae (I) and (II) is preferable. Also preferable is acopolymer using both of the polymerizable monomers represented by thegeneral formulae (I) and (II). The polymerizable monomers represented bythe general formulae (I) and (II) may be copolymerized with otherpolymerizable monomers such as acrylic acid, acrylic esters of C₁ toC₁₈, methacrylic acid, methacrylic acid esters of C₁ to C₁₈, acrylamide,vinyl alcohol, acrylonitrile, vinyl pyrrolidone, vinyl pyridine, vinylacetate, maleic acid, fumaric acid, itaconic acid, andp-styrenecarboxylic acid. The polymer or copolymer preferably has aweight average molecular weight of 500 or more, and is preferablyprepared by radical polymerization or the like.

In the general formula (I), R₁ represents a hydrogen atom, methyl group,phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, and R₂ and R₃ each independentlyrepresents a hydrogen atom, alkyl chain of C₁ to C₁₈, methylol group, oracetyl group with the proviso that the case where both of themsimultaneously represent a hydrogen atomis excluded. In the generalformula (II), R₁ represents a hydrogen atom, methyl group, phenyl group,benzyl group, chloro group, difluoromethyl group, trifluoromethyl group,or cyano group, R₄ represents a morpholino group, thiomorpholino group,pyrrolidino group, or piperidino group.

Examples of the water-soluble polymer having a N-monosubstituted orN,N-disubstituted skeleton include: compounds having a N-monosubstitutedskeleton such as N-methylacrylamide, N-ethylacrylamide,N-propylacrylamide, N-isopropylacrylamide, N-butylacrylamide,N-isobutylacrylamide, N-tertiarybutylacrylamide, N-heptylacrylamide,N-octylacrylamide, N-tertiaryoctylacrylamide, N-dodecylacrylamide,N-octadecylacrylamide, N-methylolacrylamide, N-acetylacrylamide,N-diacetone acrylamide, N-methylmethacrylamide, N-ethylmethacrylamide,N-propylmethacrylamide, N-isopropylmethacrylamide,N-butylmethacrylamide, N-isobutylmethacrylamide,N-tertiarybutylmethacrylamide, N-heptylmethacrylamide,N-octylmethacrylamide, N-tertiaryoctylmethacrylamide,N-dodecylmethacrylamide, N-octadecylmethacrylamide,N-methylolmethacrylamide, N-acetylmethacrylamide, and N-diacetonemethacrylamide; and compounds having a N,N-disubstituted skeleton suchas N,N-dimethylacrylamide, N,N-diethylacrylamide,N,N-dipropylacrylamide, N,N-diisopropylacrylamide,N,N-dibutylacrylamide, N,N-diisobutylacrylamide,N,N-ditertiarybutylacrylamide, N,N-diheptylacrylamide,N,N-dioctylacrylamide, N,N-ditertiaryoctylacrylamide,N,N-didodecylacrylamide, N,N-dioctadecylacrylamide,N,N-dimethylolacrylamide, N,N-diacetylacrylamide, N,N-diacetoneacrylamide, N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide,N,N-dipropylmethacrylamide, N,N-diisopropylmethacrylamide,N,N-dibutylmethacrylamide, N,N-diisobutylmethacrylamide,N,N-ditertiarybutylmethacrylamide, N,N-diheptylmethacrylamide,N,N-dioctylmethacrylamide, N,N-ditertiaryoctylmethacrylamide,N,N-didodecylmethacrylamide, N,N-dioctadecylmethacrylamide,N,N-dimethylolmethacrylamide, N,N-diacetylmethacrylamide, N,N-diacetonemethacrylamide, acryloylpiperidine, acryloylmorpholine,acryloylthiomorpholine, and acryloylpyrrolidine. These compounds may beused alone or in combination of two or more of them.

Other examples of the polysilicon film polishing inhibitor of theinvention include polyethylene glycol which is a water-soluble polymer.

Other examples of the polysilicon film polishing inhibitor of theinvention also include an oxyethylene adduct of an acetylene-based diolwhich is a water-soluble polymer. Examples of the oxyethylene adduct ofan acetylene-based diol include compounds such as2,4,7,9-tetramethyl-5-decyne-4,7-diol,2,4,7,9-tetramethyl-5-decyne-4,7-diol-dipolyoxyethylene ether, and2,4,7,9-tetramethyl-5-decyne-4,7-diol-monopolyoxyethylene ether. Amongthem, 2,4,7,9-tetra methyl-5-decyne-4, 7-diol-dipolyoxyethylene ether isparticularly preferable from the view point of both of water solubilityand decrease of surface tension.

Other examples of the polysilicon film polishing inhibitor of theinvention also include a compound represented by the following generalformula (III) and/or an organic compound having an acetylene bondrepresented by the following general formula (IV).

[Formula 11]R¹—C≡C—R²  (III)

(In the general formula (III), R¹ represents a hydrogen atom orsubstituted or unsubstituted alkyl group having 1 to 5 carbon atoms, R²represents a substituted or unsubstituted alkyl group having 4 to 10carbon atoms.)

(In the general formula (IV), R³ to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)

Other examples of the polysilicon film polishing inhibitor of theinvention also include an alkoxylated linear aliphatic alcohol.

The pH of the polishing slurry using the polysilicon film polishinginhibitor is preferably 5.0 or more and 8.0 or less, and more preferably6.0 or more and 7.0 or less. If the pH is less than 5, the polishingrate for a polysilicon film tends to increase, and if the pH is morethan 8, the polishing rate for a silicon oxide film tends to decrease.

In the invention, the pH of the polishing slurry is measured as follows:two-point calibration is performed using standard buffer solutions(phthalate pH buffer solution having a pH of 4.21 (25° C.) and a neutralphosphate pH buffer solution having a pH of 6.86 (25° C.)) with a pHmeter (e.g., model number PH81 manufactured by Yokogawa ElectricCorporation), subsequently the electrode is immersed in the polishingslurry, and the pH is measured after it becomes stable after a lapse ofat least two minutes. The pH may be adjusted with an alkaline componentor acid such as ammonia or tetramethyl ammonium hydroxide (TMAH).

The polysilicon film polishing inhibitor may be used alone, butpreferably in combination of two or more of them, and particularlypreferably contains two or more members selected from the water-solublepolymer compound having a N-monosubstituted or N,N-disubstitutedskeleton substituted by any member selected from the group consisting ofacrylamide, methacrylamide, and α-substituted derivatives thereof,polyethylene glycol, an oxyethylene adduct of an acetylene-based diol, acompound represented by the general formula (III), a compoundrepresented by the general formula (IV), and an alkoxylated linearaliphatic alcohol.

The addition amount of the polysilicon film polishing inhibitor ispreferably in the range of 0.005% by mass or more and 2% by mass or lessrelative to 100 parts by mass of the polishing slurry, or 0.005 to 2% bymass in the polishing slurry. If the amount is less than 0.005% by mass,the inhibitory effect on polishing of a polysilicon film is low, and ifmore than 2% by mass, the polishing rate for a silicon oxide film maydecrease, and flowability may deteriorate due to gelation.

Examples of other polysilicon film polishing inhibitors which may beused in the invention include polyvinyl pyrrolidone or copolymerscontaining vinyl pyrrolidone (hereinafter they are collectively referredto as polyvinyl pyrrolidones). The addition amount of polyvinylpyrrolidones is preferably in the range of 0.005% by mass or more and 5%by mass or less relative to the polishing slurry. The weight averagemolecular weight of polyvinyl pyrrolidones is preferably 10,000 to1,200,000. If the molecular weight is less than 10,000, planarizationproperty tends to be insufficient, and if more than 1,200,000, theabrasive tends to cause aggregation. The pH of the polishing slurryusing a polyvinyl pyrrolidone is preferably 5.0 or more and 12.0 orless, and more preferably 6.0 or more and 7.0 or less. If the pH is lessthan 5.0, the polishing rate for a polysilicon film tends to beexcessive, and if the pH is more than 12, the polishing rate for apolysilicon film tends to decrease. The polyvinyl pyrrolidones may becombined with the above-described polysilicon film polishing inhibitor.

The polishing slurry of the invention may be combined with otherwater-soluble polymers. Examples of the other water-soluble polymers arenot particularly limited, and include polysaccharides such as alginicacid, pectin acid, carboxy methyl cellulose, agar, curdlan and pullulan;polycarboxylic acids and salts thereof such as polyasparatic acid,polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid,polymethacrylic acid ammonium salt, polymethacrylic acid sodium:salt,polyamide acid, polymaleic acid, polyitaconic acid, polyfumaric acid,poly(p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, polyacrylic acid ammonium salt, sodium polyacrylatesalt, polyamide acid, polyamide acid ammonium salt, polyamide acidsodium salt, and polyglyoxalic acid; and vinyl polymers such aspolyvinyl alcohol and polyacrolein. The weight average molecular weightis preferably 500 or more, and preferably 50,000 or less for avoidingthe occurrence of excessive viscosity and deterioration of thepreservation stability of the polishing slurry.

In particular, it is preferable to use at least one selected frompolyacrylic acid, polyacrylate, and copolymer containing acrylate as anadditive for improving the flatness of the oxide film surface. Theaddition amount of the polyacrylic acid, polyacrylate, and copolymercontaining acrylate is preferably in the range of 0.01% by mass or moreand 5% by mass or less relative to 100 parts by mass of the polishingslurry. This is because that if the amount is less than 0.01% by mass,the effect of improving the flatness is low, and if more than 5% bymass, the abrasive tends to cause aggregation.

Further, the polysilicon film polishing inhibitor may be combined withthe additive for improving global flatness. More specifically, thewater-soluble polysilicon film polishing inhibitor will not cause anyproblem even if it is combined with an additive for improving flatnesscontaining a copolymer containing polyacrylic acid, polyacrylate, oracrylate.

The additive liquid for polishing slurry of the invention is an additiveliquid for polishing slurry used in a polishing slurry for polishing asilicon oxide film on polysilicon, and contains a polysilicon polishinginhibitor and water.

The polishing slurry for silicon oxide of the invention may be preservedas a two-liquid polishing slurry in which a slurry containing anabrasive and water is separated from an additive liquid containing apolysilicon polishing inhibitor and water, or may be preserved as aone-liquid polishing slurry containing an additive liquid or apolysilicon polishing inhibitor. When the polishing slurry is preservedas a two-liquid polishing slurry, its planarization property andpolishing rate can be adjusted by arbitrarily changing the formulationof the two-liquids. When a substrate is polished with the two-liquidpolishing slurry, the additive liquid and the slurry are sent indifferent lines, and the lines are merged into one to mix the liquidsimmediately before the outlet of the feeding line, and the mixture issupplied onto the polishing platen, or the additive is mixed with theslurry immediately before polishing. For two-liquid polishing slurries,the additive for improving flatness is preferably contained in theadditive liquid.

Examples of the method for preparing a silicon oxide film which can bepolished with the polishing slurry of the invention include alow-pressure CVD method and a plasma CVD method. Formation of a siliconoxide film by the low-pressure CVD method is achieved by an oxidationreaction of SiH₄—O₂ system at a low temperature of 400° C. or lowerusing monosilane (SiH₄) as an Si source, and oxygen (O₂) as an oxygensource. According to circumstances, CVD may be followed by heattreatment at a temperature of 1000° C. or lower. When phosphorus (P) isdoped in order to planarize the surface by high-temperature reflowing,it is preferable to use a reaction gas of SiH₄—O₂—PH₃ system. The plasmaCVD method has an advantage that any chemical reaction which requires ahigh temperature under normal heat equilibrium can be carried out at alow temperature. There are two types of methods for generating plasma:capacitive coupling type and inductive coupling type. Examples of thereaction gas include a gas of SiH₄—N₂O system using SiH₄ as an Si sourceand N₂O as an oxygen source, and a gas of TEOS—O₂ system usingtetraethoxysilane (TEOS) as an Si source (TEOS-plasma CVD method). Thesubstrate temperature is preferably in the range of 250 to 400° C., andthe reaction pressure is preferably in the range of 67 to 400 Pa. Thus,the silicon oxide film may be doped with an element such as phosphorusor boron.

In the same manner, formation of a polysilicon film by the CVD method isperformed using SiH₄ as an Si source at a substrate temperature of 600to 1000° C.

The polishing method of the invention is a method for polishing anobject to be polished, wherein the object to be polished is held againsta polishing pad with its surface to be polished facing the polishingpad, and polished by being slid relative to the polishing pad while apolishing slurry is supplied between the polishing pad and the surfaceto be polished, and the polishing slurry for silicon oxide of theinvention is used as the polishing slurry. Examples of the object to bepolished include a substrate involved in the manufacture of asemiconductor device, for example a substrate comprising a polysiliconfilm having formed thereon a silicon oxide film.

The ratio of the polishing rate for a silicon oxide film to thepolishing rate for a polysilicon film (selective ratio) is preferably 10or more from the viewpoint of easy stop control of polishing. Thepolishing rate for a silicon oxide film is preferably 50 nm/min or more,and more preferably 100 nm/min or more. The polishing rate forpolysilicon is preferably 10 nm/min or less, and more preferably 5nm/min or less. The polishing apparatus may be a common polishingapparatus comprising a holder for holding a substrate and a platenequipped with a motor or the like with variable rotation number, towhich a polishing cloth (pad) can be attached. The polishing cloth maybe a common nonwoven fabric, foamed polyurethane, or porous fluorocarbonresin, and is not particularly limited. The polishing cloth ispreferably groove-processed for retaining the polishing slurry.

The polishing conditions are not limited, but the rotation rate of theplaten is preferably as lows as 200 min⁻¹ or less for preventing thesubstrate from jumping out, and the pressure to be applied to thesubstrate is preferably 9.8×10⁴ Pa or less in order to prevent thedevelopment of scratches. During polishing, the polishing slurry iscontinuously supplied to the polishing cloth with a pump or the like.The amount of the polishing slurry to be supplied is not particularlylimited, but is preferably in an amount so that the surface of thepolishing cloth is constantly covered with the polishing slurry. Thesubstrate after completion of polishing is preferably thoroughly washedin running water, and dried after water droplets adhering to thesubstrate are knocked off with a spin dryer or the like.

EXAMPLES

The invention is further illustrated by following Examples. Theinvention is not limited to these Examples.

(Preparation of Cerium Oxide Particles)

2 kg of cerium carbonate hydrate was placed in a container made ofplatinum, followed by sintering at 800° C. for 2 hours in air to obtainabout 1 kg of a yellowish white powder. Phase identification of thispowder was made by X-ray diffractometry to confirm that it was ceriumoxide. The sintered powder had particle diameters of 30 to 100 μm. Thesurface of the sintered particles was observed with a scanning electronmicroscope, where grain boundaries of cerium oxide were seen. Diametersof cerium oxide primary particles surrounded by the grain boundarieswere measured to find that the median diameter and maximum diameter intheir particle size distribution were 190 nm and 500 nm, respectively. 1kg of the cerium oxide powder was pulverized by a dry process with a jetmill. The pulverized particles were observed with a scanning electronmicroscope to find that large pulverization residue particles of 1 μm to3 μm and pulverization residue particles of 0.5 μm to 1 μm were presentin a mixed state in addition to small particles having the same size asthe primary particle diameter.

(Preparation of Cerium Oxide Slurry)

1 kg of the cerium oxide particles prepared above was mixed with 23 g ofan aqueous solution of polyacrylic acid ammonium salt (40% by mass) and8977 g of deionized water, followed by ultrasonic dispersion for 10minutes while being stirred. The obtained slurry was filtered through a1-micron filter, and followed by further addition of deionized water toobtain a 5% by mass slurry. The slurry had a pH of 8.3. The slurry wasdiluted to an appropriate concentration in order to examine the slurryparticles with a laser diffraction particle size analyzer to find thatthe median value of the particle diameter was 190 nm.

(Procurement of Water-Soluble Polymer)

Water-Soluble Polymer 1

Polyvinyl pyrrolidone manufactured by Wako Pure Chemical Industries,Ltd. (reagent, K-30) was procured.

Water-Soluble Polymer 2

Polyvinyl pyrrolidone manufactured by Wako Pure Chemical Industries,Ltd. (reagent, K-90) was procured.

Water-Soluble Polymer 3-1 [Synthesis Example 1]

280 g of deionized water and 20 g of 2-propanol were placed in a 1-Lflask, heated to 90° C. while being stirred in a nitrogen gasatmosphere, followed by injection of a solution of 1 g of apolymerization initiator (trade name: V-601, manufactured by Wako PureChemical Industries, Ltd.) in 100 g acryloyl morpholine over a period of2 hours. Subsequently the flask was incubated at 90° C. for 5 hours,cooled, and taken out to obtain a water-soluble polymer solution. Theconcentration of the water-soluble polymer in the solution was 25.3%.

Water-Soluble Polymer 3-2 [Synthesis Example 2]

Synthesis was carried out using 50 g of N,N-diethylacrylamide and 50 gof acryloyl morpholine by the method of Synthesis example 1 to obtain awater-soluble polymer solution. The concentration of the water-solublepolymer in the solution was 25.1%.

Water-Soluble Polymer 3-3 [Synthesis Example 3]

Synthesis was carried out using 50 g of N,N-diethylacrylamide and 50 gof N,N-dimethylacrylamide by the method of Synthesis example 1 to obtaina water-soluble polymer solution. The concentration of the water-solublepolymer in the solution was 25.0%.

Water-Soluble Polymer 3-4 [Synthesis Example 4]

Synthesis was carried out using 100 g of N,N-dimethylacrylamide by themethod of Synthesis example 1 to obtain a water-soluble polymersolution. The concentration of the water-soluble polymer in the solutionwas 25.1%.

Water-Soluble Polymer 4

Polyethylene glycol manufactured by Dai-Ichi Kogyo Seiyaku Co., Ltd.(reagent, PEG-4000) was procured.

Water-Soluble Polymer 5

As an oxyethylene adduct of an acetylene-based diol,2,4,7,9-tetramethyl-5-decyne-4,7-diol was procured.

Water-Soluble Polymer 6

As an alkoxylated linear aliphatic alcohol, a reagent manufactured byBASF (LF-401) was procured.

Water-Soluble Polymer 7

Polyacrylic acid (trade name: JULIMER AC-10S, manufactured byNihonjunyaku Co., Ltd.) was procured.

(Preparation of Polishing Slurry)

Polishing Slurry 1

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 1 g of polyvinyl pyrrolidone of the water-solublepolymer 1 as a polysilicon film polishing inhibitor and 2399 g ofdeionized water to obtain a polishing slurry (cerium oxide: 1% by mass).The polishing slurry was adjusted to pH 6.5 with a trace amount ofnitric acid.

Polishing Slurry 2

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 2 g of polyvinyl pyrrolidone of the water-solublepolymer 2 as a polysilicon film polishing inhibitor and 2398 g ofdeionized water to obtain a polishing slurry (cerium oxide: 1% by mass).The polishing slurry was adjusted to pH 6.5 with a trace amount ofnitric acid.

Polishing Slurry 3

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 0.5 g of polyvinyl pyrrolidone of the water-solublepolymer 1 as a polysilicon film polishing inhibitor, 70 g of a solutionof the water-soluble polymer 7 as a highly planarizing agent for oxidefilm, and 2329.5 g of deionized water to obtain a polishing slurry(cerium oxide: 1% by mass). The polishing slurry was adjusted to pH 6.5with a trace amount of ammonia.

Polishing Slurry 4

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 20 g of a solution of the water-soluble polymer 3-1(synthesis example 1) as a polysilicon polishing inhibitor and 2380 g ofdeionized water to obtain a polishing slurry (cerium oxide: 1% by mass).The polishing slurry was adjusted to pH 6.5 with a trace amount ofnitric acid.

Polishing Slurry 5

A polishing slurry was prepared in the same manner as polishing slurry 4except that a solution of the water-soluble polymer 3-2 (synthesisexample 2) was used as a polysilicon polishing inhibitor in place of thewater-soluble polymer 3-1 (synthesis example 1).

Polishing Slurry 6

A polishing slurry was prepared in the same manner as polishing slurry 4except that a solution of the water-soluble polymer 3-3 (synthesisexample 3) was used as a polysilicon polishing inhibitor in place of thewater-soluble polymer 3-1 (synthesis example 1).

Polishing Slurry 7

A polishing slurry was prepared in the same manner as polishing slurry 4except that a solution of the water-soluble polymer 3-4 (synthesisexample 4) was used as a polysilicon polishing inhibitor in place of thewater-soluble polymer 3-1 (synthesis example 1).

Polishing Slurry 8

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 10 g of a solution of the water-soluble polymer 3-1(synthesis example 1) as a polysilicon film polishing inhibitor, 70 g ofa solution of the water-soluble polymer 7 as a highly planarizing agentfor oxide film, and 2320 g of deionized water to obtain a polishingslurry (cerium oxide: 1% by mass). The polishing slurry was adjusted topH 6.5 with a trace amount of ammonia.

Polishing Slurry 9

A polishing slurry was prepared in the same manner as polishing slurry 8except that a solution of the water-soluble polymer 3-4 (synthesisexample 4) was used as a polysilicon polishing inhibitor in place of thewater-soluble polymer 3-1 (synthesis example 1).

Polishing Slurry 10

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 5 g of a solution of the water-soluble polymer 4 asa polysilicon film polishing inhibitor, 70 g of a solution of thewater-soluble polymer 7 as a highly planarizing agent for oxide film,and 2325 g of deionized water to obtain a polishing slurry (ceriumoxide: 1% by mass). The polishing slurry was adjusted to pH 6.5 with atrace amount of ammonia.

Polishing Slurry 11

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 5 g of a solution of the water-soluble polymer 5 asa polysilicon film polishing inhibitor, 70 g of a solution of thewater-soluble polymer 7 as a highly planarizing agent for oxide film,and 2325 g of deionized water to obtain a polishing slurry (ceriumoxide: 1% by mass). The polishing slurry was adjusted to pH 6.5 with atrace amount of ammonia.

Polishing Slurry 12

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 5 g of a solution of the water-soluble polymer 6 asa polysilicon film polishing inhibitor, 70 g of a solution of thewater-soluble polymer 7 as a highly planarizing agent for oxide film,and 2325 g of deionized water to obtain a polishing slurry (ceriumoxide: 1% by mass). The polishing slurry was adjusted to pH 6.5 with atrace amount of ammonia.

Polishing Slurry 13

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 2400 g of deionized water to obtain a polishingslurry (cerium oxide: 1% by mass). The polishing slurry was adjusted topH 6.5 with a trace amount of ammonia.

Polishing Slurry 14

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 70 g of a solution of the water-soluble polymer 7as a highly planarizing agent for oxide film and 2320 g of deionizedwater to obtain a polishing slurry (cerium oxide: 1% by mass). Thepolishing slurry was adjusted to pH 6.5 with a trace amount of ammonia.

Polishing Slurry 15

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 12 g of a solution of the water-soluble polymer 3-1(synthesis example 1) as a polysilicon polishing inhibitor and 2388 g ofdeionized water to obtain a polishing slurry (cerium oxide: 1% by mass).The polishing slurry was adjusted to pH 4.5 with a trace amount ofnitric acid.

Polishing Slurry 16

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 60 g of a solution of the water-soluble polymer 3-1(synthesis example 1) as a polysilicon polishing inhibitor and 2340 g ofdeionized water to obtain a polishing slurry (cerium oxide: 1% by mass).The polishing slurry was adjusted to pH 9.0 with a trace amount ofammonia.

Polishing Slurry 17

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 2400 g of deionized water to obtain a polishingslurry (cerium oxide: 1% by mass). The polishing slurry was adjusted topH 4.5 with a trace amount of nitric acid.

Polishing Slurry 18

600 g of the cerium oxide slurry prepared above (solid content: 5% bymass) was mixed with 2400 g of deionized water to obtain a polishingslurry (cerium oxide: 1% by mass). The polishing slurry was adjusted topH 9.0 with a trace amount of ammonia. Tables 1 through 3 show thecomposition and pH of the polishing slurries.

(Evaluation of Polishing)

Example 1

The substrate below was subjected to CMP polishing under followingconditions while a polishing slurry of the polishing slurry 1 wasdropped on the pad attached to the platen, and evaluated as describedbelow.

<Substrates for Evaluation>

Substrate 1: A blanket substrate of 8 inch diameter comprising a Sisubstrate having formed thereon a silicon oxide film (P—TEOS) of 0.8 μmthickness.

Substrate 2: A blanket substrate of 8 inch diameter comprising a Sisubstrate having formed thereon a silicon oxide film of 0.1 μm thicknessand a polysilicon film of 0.4 μm thickness in this order.

<Evaluation Conditions>

Polishing apparatus: MIRRA polishing machine, manufactured by AMAT,platen diameter 600 mm, rotary type

Polishing pad: IC-1000/Suba 400 manufactured by Nitta Haas Incorporated,foamed double layer pad with a concentric groove

Polishing pressure: 25 kPa

Platen rotation number: 98 min⁻¹

Polishing slurry flow rate: 200 ml/min

Polishing time: 1 min

<Evaluation Item and Evaluation Method>

Silicon oxide polishing rate by CMP: Difference in the film thickness ofthe substrate 1 before and after CMP was determined with an optical filmthickness measuring device.

Polysilicon polishing rate by CMP: Difference in the film thickness ofthe substrate 2 before and after CMP was determined with an optical filmthickness measuring device.

The results of the evaluation indicate that the polishing rate for asilicon oxide film was 160 nm/min, the polishing rate for a polysiliconwas 0.7 nm/min, and the ratio of the polishing rate for a silicon oxidefilm to the polishing rate for a polysilicon film was 228.

Example 2

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 2 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 250 nm/min, thepolishing rate for a polysilicon was 1.5 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 167.

Example 3

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 3 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 90 nm/min, thepolishing rate for a polysilicon was 3.5 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 26.

Example 4

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 4 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 270 nm/min, thepolishing rate for a polysilicon was 1.2 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 225.

Example 5

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 5 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 250 nm/min, thepolishing rate for a polysilicon was 1 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 250.

Example 6

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 6 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 200 nm/min, thepolishing rate for a polysilicon was 1.5 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 133.

Example 7

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 7 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 190 nm/min, thepolishing rate for a polysilicon was 1.1 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 173.

Example 8

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 8 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 160 nm/min, thepolishing rate for a polysilicon was 0.8 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 200.

Example 9

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 3 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 170 nm/min, thepolishing rate for a polysilicon was 1 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 170.

Example 10

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 10 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 180 nm/min, thepolishing rate for a polysilicon was 1 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 180.

Example 11

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 11 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 180 nm/min, thepolishing rate for a polysilicon was 2 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 90.

Example 12

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 12 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 150 nm/min, thepolishing rate for a polysilicon was 1 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 150.

Comparative Example 1

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 13 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 410 nm/min, thepolishing rate for a polysilicon was 90 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 4.6.

Comparative Example 2

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 14 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 260 nm/min, thepolishing rate for a polysilicon was 60 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 4.3.

Example 13

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 15 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 22 nm/min, thepolishing rate for a polysilicon was 0.8 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 27.5.

Example 14

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 16 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 280 nm/min, thepolishing rate for a polysilicon was 35 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 8.0.

Comparative Example 3

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 17 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 435 nm/min, thepolishing rate for a polysilicon was 75 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 5.8.

Comparative Example 4

The polishing rates for a silicon oxide film and a polysilicon film wereevaluated using a polishing slurry of the polishing slurry 18 under thesame conditions as Example 1. The results of the evaluation indicatethat the polishing rate for a silicon oxide film was 432 nm/min, thepolishing rate for a polysilicon was 110 nm/min, and the ratio of thepolishing rate for a silicon oxide film to the polishing rate for apolysilicon film was 3.9. Tables 1 through 3 show the polishing rate andpolishing rate ratio of Examples and Comparative Examples. TABLE 1 Ex. 1Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Polishing slurry 1 2 3 4 5 6 7Cerium oxide (5 wt %) 600 600 600 600 600 600 600 Water-soluble polymer1 1 — 0.5 — — — — Water-soluble polymer 2 — 2 — — — — — Water-solublepolymer 3-1 — — — 20 — — — Water-soluble polymer 3-2 — — — — 20 — —Water-soluble polymer 3-3 — — — — — 20 — Water-soluble polymer 3-4 — — —— — — 20 Water-soluble polymer 7 — — 70 — — — — Deionized water 23992398 2329.5 2380 2380 2380 2380 pH 6.5 6.5 6.5 6.5 6.5 6.5 6.5 Polishingrate for silicon oxide (nm/minute) 160 250 90 270 250 200 190 Polishingrate for polysilicon (nm/minute) 0.7 1.5 3.5 1.2 1 1.5 1.1 Polishingrate ratio of silicon oxide to polysilicon 228 167 26 225 250 133 173

TABLE 2 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Polishing slurry 8 9 10 11 12Cerium oxide (5 wt %) 600 600 600 600 600 Water-soluble polymer 1 — — —— — Water-soluble polymer 2 — — — — — Water-soluble polymer 3-1 10 — — —— Water-soluble polymer 3-2 — — — — — Water-soluble polymer 3-3 — — — —— Water-soluble polymer 3-4 — 10 — — — Water-soluble polymer 4 — — 5 — —Water-soluble polymer 5 — — — 5 — Water-soluble polymer 6 — — — — 5Water-soluble polymer 7 70 70 70 70 70 Deionized water 2320 2320 23252325 2325 pH 6.5 6.5 6.5 6.5 6.5 Polishing rate for silicon oxide(nm/minute) 160 170 180 180 150 Polishing rate for polysilicon(nm/minute) 0.8 1 1 2 1 Polishing rate ratio of silicon oxide topolysilicon 200 170 180 90 150

TABLE 3 Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 13 Ex. 14 Ex. 3 Ex. 4Polishing slurry 13 14 15 16 17 18 Cerium oxide (5 wt %) 600 600 600 600600 600 Water-soluble polymer 1 — — — — — — Water-soluble polymer 2 — —— — — — Water-soluble polymer 3-1 — — 12 60 — — Water-soluble polymer3-2 — — — — — — Water-soluble polymer 3-3 — — — — — — Water-solublepolymer 3-4 — — — — — — Water-soluble polymer 7 — 70 — — — — Deionizedwater 2400 2330 2388 2340 2400 2400 pH 6.5 6.5 4.5 9.0 4.5 9.0 Polishingrate for silicon oxide (nm/minute) 410 260 22 280 435 432 Polishing ratefor polysilicon (nm/minute) 90 60 0.8 35 75 110 Polishing rate ratio ofsilicon oxide to polysilicon 4.6 4.3 27.5 8.0 5.8 3.9

Examples 1 through 14 of the invention exhibited a high polishing ratefor a silicon oxide film and a low polishing rate for polysilicon, andachieved a sufficiently large polishing rate ratio between a siliconoxide film and polysilicon, wherein polysilicon is applicable as astopper. The polishing rate for an oxide film was rather low at pH 4.5in Example 13, and the polishing rate for a polysilicon film was ratherhigh at pH 9 in Example 14, indicating that higher practicality isachieved in the range of pH 5 to 8. On the other hand, in ComparativeExamples 1, 3, and 4 in which no polysilicon polishing inhibitor wasused, the polishing rate for a silicon oxide film was high, but thepolishing rate for polysilicon was also high, wherein polysilicon isinapplicable as a stopper. In Comparative Example 2 in which nopolysilicon polishing inhibitor was used but an additive was used, thepolishing rate for polysilicon was so high that the polishing rate ratiobetween a silicon oxide film and polysilicon was not large.

As described above, the invention provides a polishing slurry and apolishing method which are capable of polishing a silicon oxide film ona polysilicon film at a high speed, and inhibiting the progress ofpolishing of a polysilicon film in exposed parts in a CMP technique inthe manufacturing process of a semiconductor in which a silicon oxidefilm is polished.

1. A polishing slurry for silicon oxide for polishing a silicon oxidefilm on polysilicon, which contains an abrasive, a polysilicon polishinginhibitor, and water.
 2. The polishing slurry for silicon oxideaccording to claim 1, wherein the ratio of the polishing rate forsilicon oxide to that for polysilicon is 10 or more.
 3. The polishingslurry for silicon oxide according to claim 1 or 2, wherein thepolysilicon polishing inhibitor is a water-soluble polymer having aN-monosubstituted or N,N-disubstituted skeleton substituted by anymember selected from the group consisting of acrylamide, methacrylamide,and α-substituted derivatives thereof.
 4. The polishing slurry forsilicon oxide according to claim 3, wherein the water-soluble polymer isa polymer or copolymer containing at least one selected from the groupconsisting of a polymerizable monomer represented by the followinggeneral formula (I) and a polymerizable monomer represented by thefollowing general formula (II).

(In the general formula (I), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, and R₂ and R₃ each independentlyrepresents a hydrogen atom, alkyl chain of C₁ to C₁₈, methylol group, oracetyl group with the proviso that the case where both of themsimultaneously represent a hydrogen atom is excluded.)

(In the general formula (II), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, R₄ represents a morpholino group,thiomorpholino group, pyrrolidino group, or piperidino group.)
 5. Thepolishing slurry for silicon oxide according to claim 1 or 2, whereinthe polysilicon polishing inhibitor is polyethylene glycol.
 6. Thepolishing slurry for silicon oxide according to claim 1 or 2, whereinthe polysilicon polishing inhibitor is an oxyethylene adduct of aacetylene-based diol.
 7. The polishing slurry for silicon oxideaccording to claim 1 or 2, wherein the polysilicon polishing inhibitoris at least either of the compound represented by the following generalformula (III) and the compound and represented by the following generalformula (IV). [Formula 3]R¹—C≡C—R²  (III) (In the general formula (III), R¹ represents a hydrogenatom or substituted or unsubstituted alkyl group having 1 to 5 carbonatoms, R² represents a substituted or unsubstituted alkyl group having 4to 10 carbon atoms.)

(In the general formula (IV), R³ to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)
 8. The polishingslurry for silicon oxide according to claim 1 or 2, wherein thepolysilicon polishing inhibitor is an alkoxylated linear aliphaticalcohol.
 9. The polishing slurry for silicon oxide according to any ofclaims 1 or 2, which contains two or more types of the polysiliconpolishing inhibitor.
 10. The polishing slurry for silicon oxideaccording to claim 9, wherein the polysilicon polishing inhibitorincludes two or more compounds selected from a water-soluble polymerhaving a N-monosubstituted or N,N-disubstituted skeleton substituted byany member selected from the group consisiting of acrylamide,methacrylamide, and α-substituted derivatives thereof, polyethyleneglycol, an oxyethylene adduct of an acetylene-based diol, a compoundrepresented by the following general formula (III), a compoundrepresented by the following general formula (IV), and an alkoxylatedlinear aliphatic alcohol. [Formula 9]R¹—C≡C—R²  (III) (In the general formula (III), R¹ represents a hydrogenatom or substituted or unsubstituted alkyl group having 1 to 5 carbonatoms, R² represents a substituted or unsubstituted alkyl group having 4to 10 carbon atoms.)

(In the general formula (IV), R³ to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)
 11. The polishingslurry for silicon oxide according to claim 3, wherein the content ofthe polysilicon polishing inhibitor is 0.005% by mass or more and 2% bymass or less.
 12. The polishing slurry for silicon oxide according toclaim 3, wherein the pH is 5.0 to 8.0.
 13. The polishing slurry forsilicon oxide according to any of claims 1 or 2, which contains at leastone selected from polyacrylic acid, polyacrylate, and a copolymercontaining acrylate.
 14. The polishing slurry for silicon oxideaccording to any of claims 1 or 2, wherein the abrasive contains ceriumoxide.
 15. The polishing slurry for silicon oxide according to claim 1or 2, wherein the polysilicon polishing inhibitor contains polyvinylpyrrolidone or a copolymer containing vinyl pyrrolidone.
 16. Thepolishing slurry for silicon oxide according to claim 15, wherein thecontent of the polysilicon polishing inhibitor is 0.005 to 5% by mass.17. The polishing slurry for silicon oxide according to claim 15,wherein the pH is 5.0 to 12.0.
 18. The polishing slurry for siliconoxide according to claim 15, which contains at least one selected frompolyacrylic acid, polyacrylate, or a copolymer containing acrylate. 19.The polishing slurry for silicon oxide according to claim 15, whereinthe abrasive contains cerium oxide.
 20. The polishing slurry for siliconoxide according to claim 13, wherein the content of at least oneselected from polyacrylic acid, polyacrylate, and a copolymer containingacrylate is 0.01 to 5% by mass.
 21. The polishing slurry for siliconoxide according to any of claims 1 or 2, wherein the abrasive containssilicon oxide.
 22. A method for polishing a semiconductor substrateusing the polishing slurry for silicon oxide according to claim
 1. 23.An additive liquid for polishing slurry used in a polishing slurry forpolishing a silicon oxide film on polysilicon, which contains apolysilicon polishing inhibitor and water.
 24. The additive liquid forpolishing slurry according to claim 23, wherein the polysiliconpolishing inhibitor is a water-soluble polymer having aN-monosubstituted or N,N-disubstituted skeleton substituted by anymember selected from the group consisting of acrylamide, methacrylamide,and α-substituted derivatives thereof.
 25. The additive liquid forpolishing slurry according to claim 24, wherein the water-solublepolymer is a polymer or copolymer containing at least one selected fromthe group consisting of a polymerizable monomer represented by thefollowing general formula (I) and a polymerizable monomer represented bythe following general formula (II).

(In the general formula (I), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, and R₂ and R₃ each independentlyrepresents a hydrogen atom, alkyl chain of C₁ to C₁₈, methylol group, oracetyl group with the proviso that the case where both of themsimultaneously represent a hydrogen atom is excluded.)

(In the general formula (II), R₁ represents a hydrogen atom, methylgroup, phenyl group, benzyl group, chloro group, difluoromethyl group,trifluoromethyl group, or cyano group, R₄ represents a morpholino group,thiomorpholino group, pyrrolidino group, or piperidino group.)
 26. Theadditive liquid for polishing slurry according to claim 23, wherein thepolysilicon polishing inhibitor is polyethylene glycol.
 27. The additiveliquid for polishing slurry according to claim 23, wherein thepolysilicon polishing inhibitor is an oxyethylene adduct of anacetylene-based diol.
 28. The additive liquid for polishing slurryaccording to claim 23, wherein the polysilicon polishing inhibitor is atleast either of the compound represented by the following generalformula (III) and the compound and represented by the following generalformula (IV). [Formula 7]R¹—C≡C—R²  (III) (In the general formula (III), R¹ represents a hydrogenatom or substituted or unsubstituted alkyl group having 1 to 5 carbonatoms, R² represents a substituted or unsubstituted alkyl group having 4to 10 carbon atoms.)

(In the general formula (IV), R³ to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)
 29. The additiveliquid for polishing slurry according to claim 23, wherein thepolysilicon polishing inhibitor is an alkoxylated linear aliphaticalcohol.
 30. The additive liquid for polishing slurry according to anyof claims 23 through 29, which contains two or more types of thepolysilicon polishing inhibitor.
 31. The additive liquid for polishingslurry according to claim 30, wherein the polysilicon polishinginhibitor includes two or more compounds selected from a water-solublepolymer having a N-monosubstituted or N,N-disubstituted skeletonsubstituted bv any member selected from the group, consisting ofacrylamide, methacrylamide, and α-substituted derivatives thereof,polyethylene glycol, an oxyethylene adduct of an acetylene-based diol, acompound represented by the following general formula (III), a compoundrepresented by the following general formula (IV), and an alkoxylatedlinear aliphatic alcohol. [Formula 11]R¹—C≡C—R²  (III) (In the general formula (III), R¹ represents a hydrogenatom or substituted or unsubstituted alkyl group having 1 to 5 carbonatoms R² represents a substituted or unsubstituted alkyl group having 4to 10 carbon atoms.)

(In the general formula (IV), R³ to R⁶ each independently represent ahydrogen atom or substituted or unsubstituted alkyl group having 1 to 5carbon atoms, R⁷ and R⁸ each independently represent a substituted orunsubstituted alkylene group having 1 to 5 carbon atoms, and m and neach independently represents 0 or a positive number.)
 32. The additiveliquid for polishing slurry according to any of claims 23 through 29,which further contains at least one selected from polyacrylic acid,polyacrylate, and a copolymer containing acrylate.
 33. A polishingmethod using the polishing slurry for silicon oxide according to claim1, wherein the object to be polished is held against a polishing padwith the surface thereof to be polished facing the polishing pad, andpolished by being slid relative to the polishing pad while the polishingslurry is supplied between the polishing pad and the surface to bepolished.